KR100902156B1 - Light control film - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control film used in a liquid crystal display, and more particularly, to be used in a backlight unit of a liquid crystal display to improve brightness while simultaneously diffusing light emitted from a light guide plate. As a result, the manufacturing process can be significantly shortened, the cost can be reduced, a thinner liquid crystal display can be provided, and a plurality of films can be produced by stacking a plurality of films. It is possible to provide a light control film capable of preventing light loss such as optical interference phenomenon, scattering or absorption, and damage to the film.

Liquid crystal display, light control, brightness, refractive index, particle

Description

Light control film

1 is a longitudinal cross-sectional view of one preferred embodiment of the present invention;

2 is a longitudinal cross-sectional view of a general backlight unit.

[Description of main part of drawing]

10: transparent substrate layer 20: first light diffusion layer

21 light diffusing particle 30 prism layer

40: second light diffusing layer 41: light diffusing particles

The present invention relates to a light control film used in a liquid crystal display (Liquid Crystal Display).

As the industrial society has developed into an advanced information age, the importance of the electronic display device as a medium for displaying and transferring various information is increasing day by day. CRT (Cathode Ray Tube), which has been widely used in the past, has limitations due to large installation space, which makes it difficult to increase the size. Therefore, such as liquid crystal display (LCD), plasma display panel (PDP), field emission display (FED), and organic EL It is being replaced by various flat panel display devices. Among such flat panel display devices, in particular, in the case of liquid crystal display devices (LCDs), due to the advantages of thin, light, and low power consumption as a technology-intensive device in which liquid crystal and semiconductor technologies are combined, its structure and manufacturing technology have been researched and developed. In addition to the areas where liquid crystal displays have been widely used, such as notebook computers, desktop computer monitors, and portable personal communication devices (PDAs and mobile phones), large-scale technology is gradually exceeding its limitations. It is being applied as a new display device that can replace CRT, which is synonymous with display, as it is being applied to large TV of TV.

In the liquid crystal display (LCD) device, since the liquid crystal itself cannot emit light, a separate light source is installed at the rear of the device to adjust the intensity of the passing light through the liquid crystal installed in each pixel to realize contrast. do. In more detail, the liquid crystal display device is a device for controlling the light transmittance by using the electrical properties of the liquid crystal material, the uniformity and the directionality is controlled by passing through various functional prism films or sheets by emitting light from the light source lamp on the back of the device Indirect light-emitting display device that implements an image by passing light through a color filter to realize red, blue, green (R, G, B) colors, and controlling the contrast of each pixel by an electric method As a light emitting device that provides a light source, it is an important component for determining image quality such as brightness and uniformity of a liquid crystal display device.

A backlight unit BLU is widely used as the light emitting device, and a general structure thereof is as shown in FIG. 2. The backlight unit sequentially uses the light guide plate 3, the diffusion film 4, and the prism films 5 and 6 to emit light emitted using a light source 1 such as a cold cathode fluorescent lamp (CCFL). Pass it through to reach the front plate (7). Here, the light guide plate 3 transmits the light emitted from the light source 1 to be distributed over the front surface of the front plate 7 in a planar shape, and the diffusion film 4 to obtain a uniform light intensity across the entire screen. In addition, the prism films 5 and 6 perform an optical path control function for converting light rays of various directions passing through the diffusion film 4 into a range of viewing angle θ suitable for the viewer to recognize the image. In addition, the lower portion of the light guide plate 3 is provided with a reflective film 2 for increasing the efficiency of use of the light source by allowing it to be used by reflecting back the light that is not delivered to the liquid crystal panel.

In order to effectively transmit the emitted light to the liquid crystal panel, a plurality of films having various functions are mounted. A Newton's Ring phenomenon caused by mounting a plurality of films or an air layer missing from the contact surface between the films is generated. Light interference occurs such as wet-out phenomenon, light is lost through scattering or absorption as it passes through a plurality of films, and the film is damaged due to physical contact between films, resulting in lower productivity and increase in unit cost. There has been the same problem.

In the conventional prism film, diffusion particles may be provided on the back surface of the substrate layer in addition to the substrate layer and the prism layer constituting the prism film. There was a problem that the loss of light still occurs because it must pass through the substrate layer until reaching.

Accordingly, the present inventors can provide a light control film that can solve the above problems caused by stacking a plurality of films by providing the functions of a conventional diffusion film and a prism film at once, and greatly reduce the cost and manufacturing process. It was confirmed that the present invention was completed.

Accordingly, an object of the present invention is to provide a light control film capable of improving luminance while uniformly diffusing light emitted from a light guide plate.

In addition, the present invention provides a light control film that can prevent light loss, scattering or absorption of light generated by laminating a plurality of films, damage to the film, and shorten the manufacturing process and reduce cost. Its purpose is to.

The present invention for achieving the above object is a transparent substrate layer; A first light diffusion layer formed on one surface of the transparent substrate layer and including a binder resin and light diffusing particles having an average particle diameter of 0.1 to 200 μm; A prism layer formed on the first light diffusing layer; And a second light diffusing layer formed on the rear surface of the transparent base layer and including a binder resin and light diffusing particles having an average particle diameter of 0.1 to 200 μm.

The first light diffusion layer and the second light diffusion layer is characterized in that the light diffusion particles contain 0.01 to 1000 parts by weight based on 100 parts by weight of the binder resin.

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The prism layer is characterized in that it comprises any one structure selected from a linear arrangement of parallel triangular prism, a polygonal prism structure, a conical prism structure, a hemispherical prism structure and a non-spherical prism structure.

Hereinafter, with reference to the accompanying drawings the present invention will be described in more detail.

1 is a longitudinal cross-sectional view of one preferred embodiment of the present invention.

In the light control film of the present invention, the first light diffusing layer 20 is formed on one surface of the transparent base layer 10, and the prism layer 30 is formed on the other surface of the first light diffusing layer 20 to be sequentially stacked. do.

As the transparent base layer 10, a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, a polyethylene film, a polystyrene film or a polyepoxy film may be used, and mainly a polyethylene terephthalate film and a polycarbonate film are used. The transparent base layer 10 has a thickness of 10 to 1000 µm, more preferably 15 to 400 µm. If the thickness of the transparent base layer 10 is less than 10㎛ there is a problem that the mechanical strength and thermal stability is weak, if the thickness is more than 1000㎛ there is a problem that the flexibility of the film is lowered and the loss of transmitted light may occur.

The first light diffusion layer 20 formed on one surface of the transparent base layer 30 is manufactured by dispersing the light diffusion particles 21 in the binder resin.

As the binder resin, a resin having good adhesion with the transparent base layer 10 and having good compatibility with the dispersed light diffusing particles 21, that is, the light diffusing particles 21 are uniformly dispersed in the resin and separated or precipitated. Use something that is not handsome. As such resin, for example, unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydride Hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metyrolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2- Acrylic resins, such as a homopolymer of ethylhexyl acrylate, these copolymers, or a terpolymer, a urethane resin, an epoxy resin, a melamine resin, etc. are used.

The light diffusing particles 21 is used 0.01 to 1000 parts by weight based on 100 parts by weight of the binder resin, preferably 1 to 500 parts by weight. When the light diffusing particles 21 are used in less than 0.01 parts by weight, it is difficult to expect the light diffusion effect, and when the light diffusion particles are more than 1000 parts by weight, turbidity and separation of particles occur, resulting in low light diffusion efficiency.

Although the light-diffusion particles 21 vary depending on the thickness of the light-diffusion layer, the average particle diameter is suitably 0.1 to 200 µm, and preferably 0.1 to 100 µm. If the average particle diameter of the light diffusing particles 21 exceeds 200㎛ may be separated from the first light diffusing layer 20, it is because it is difficult to expect the light diffusion effect if less than 0.1㎛.

As the light diffusing particles 21, a plurality of organic particles or inorganic particles may be used. Typical organic particles used are methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylamide, metyrolacrylamide, glycidyl methacrylate, ethyl acrylate. Of acrylic particles of isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate homopolymer or copolymer and olefinic particles such as polyethylene, polystyrene, polypropylene, copolymer particles of acryl and olefinic copolymer and homopolymer After forming the particles, multi-layered multi-component particles made by covering the layers with other monomers are used. As inorganic particles, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, magnesium fluoride and the like are used. The organic and inorganic particles are merely exemplary and are not limited to the particles of the organic or inorganic materials listed above, and may be replaced by other known materials as long as the main object of the present invention can be achieved. Obviously, such material change is also within the scope of the technical idea of the present invention.

The prism layer 30 is formed on one surface of the first light diffusing layer 20. As the material constituting the prism layer 30, a polymer resin including an ultraviolet curable resin or a thermosetting resin is used, which uses a resin composition having excellent transparency and capable of forming a crosslink suitable for maintaining the shape of an optical structure. It is preferable. For example, it is possible to use an epoxy resin-ruic acid-based, polyethylol-based, unsaturated polyester-styrene, acrylic or methacrylic acid ester, and the like. Preference is given to using. Such resin types include oligomers such as polyurethane acrylics or methacrylates, epoxy acrylics or methacrylates, polyester acrylics or methacrylates, and are alone or diluted with acrylic or methacrylate monomers having a polyfunctional or monofunctional group. It is preferable to use.

The prism layer 30 in the present invention may be a linear arrangement of parallel triangular prisms as shown, and may be selected from among a polygonal prism structure, a conical prism structure, a hemispherical prism structure, and a non-spherical prism structure. As the structure of the prism layer 30 is shown, when the linear arrangement of the triangular prism is used, optical characteristics such as front luminance and light intensity distribution in the viewing angle are severely changed according to the upper vertex angle of the prism structure. The upper corner angle is preferably 80 ° to 100 °. When the angle is less than 80 °, the front luminance due to condensing is good, but the light intensity distribution in the viewing angle is difficult to apply, and when the angle is greater than 100 °, the light intensity distribution characteristic in the viewing angle is good, but the front luminance is lowered.

The present invention provides the second light diffusion layer 40 in the same manner as the first light diffusion layer 20 on the back surface where the first light diffusion layer 20 and the prism layer 30 of the transparent substrate layer 10 are not formed. By further forming, the light diffusion effect can be further improved and the brightness and hardness can be enhanced.

By manufacturing the light control film as described above, the light is first diffused while passing through the light diffusion particles 41, and then the light diffused evenly from the light diffusion particles 21 through the transparent base layer 10 immediately prism layer 30 ), The amount of light loss is greatly reduced compared to the prior art, and the manufacturing process and the cost are reduced because the separately manufactured films are manufactured at once to provide a function of light diffusion and brightness.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

<Example>

After weighing and diluting 100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene to 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.) to prepare a binder resin, spherical polymethyl methacrylate particles MH20F having an average particle diameter of 20 μm ( Kolon Corp.) 130 parts by weight of the binder resin is mixed and dispersed by a mill. The first light diffusing layer was cured for 60 seconds at 120 ° C. after coating using a gravure coater on one side of the transparent substrate layer 125 μm ultra-transparent polyethylene terephthalate film T600 (Mitsubishi). Apply.

A photosensitive composition comprising 80 parts by weight of high refractive acrylate, 15 parts by weight of 2-phenylethyl methacrylate, 3 parts by weight of 1,6-hexanediol acrylate, and 2 parts by weight of BAPO-based photoinitiator on one surface of the cured light diffusion layer. Coating the photosensitive composition applied to the light diffusion layer on the frame of the prism-shaped roller, and irradiated with ultraviolet rays (Fusion, 300 Watt / inch ² ) from the transparent substrate layer, the prism vertex angle is 90 DEG, the prism optical structure A prism layer was formed by forming a linear triangular prism having a pitch of 50 mu m and a height of the prism optical structure of 25 mu m.

In addition, 200 parts by weight of methyl ethyl ketone and 150 parts by weight of toluene were added to 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.) on the back surface of the transparent substrate layer to prepare a binder resin, and then a spherical poly having an average particle diameter of 11.5 μm. Methyl methacrylate particles MH10F (Kolon Co., Ltd.) was mixed with 20 parts by weight of the binder resin, dispersed in a mill, cured at 120 ° C. for 60 seconds, and then dried to apply a second light diffusion layer to a thickness of 13 μm to control light. A film was prepared.

Comparative Example 1

In the above embodiment, the light control film was manufactured without applying the second light diffusion layer.

Comparative Example 2

The light diffusion film and the prism film were separately prepared as follows.

That is, the light-diffusion film was diluted with 100 parts by weight of methyl ethyl ketone and 100 parts by weight of toluene in 100 parts by weight of acrylic resin 52-666 (Aekyung Chemical Co., Ltd.), and then spherical polymethyl methacrylate particles MH20F (Kolon) having an average particle diameter of 18.1 μm. G) 130 parts by weight of the acrylic resin is mixed and dispersed with a mill, and then light-diffused layer is dried to have a thickness of 20 μm after drying by using gravure on one side of a 125 μm ultra-transparent polyethylene terephthalate film (T600, Mitsubishi). By application.

On the other hand, the prism film is 80 parts by weight of high refractive acrylate, 15 parts by weight of 2-phenylethyl methacrylate, 1,6-hexanediol acrylate 3 on the back surface of the ultra-transparent polyethylene terephthalate film (T600, Mitsubishi) plastic substrate It is coated with a photosensitive composition containing a mixture of parts by weight, 2 parts by weight of BAPO-based photoinitiator, and irradiated with ultraviolet (Fusion, 300Watt / inch ² ) from the transparent base layer side of the prism vertex angle 90 °, the prism optical structure pitch 50㎛, The prism optical structure was manufactured by forming a linear triangular prism having a height of 25 μm.

Comparative Example 3

A light diffusing layer is prepared on the back surface of the light diffusing film of Comparative Example 1 in the same manner as in Example 2. A prism film is manufactured by the method similar to the said comparative example 1.

The physical property evaluation of the said Example and the comparative example was performed as mentioned later, The evaluation result is as Table 1 below.

<Luminance evaluation (Cd / ㎡)>

Two prism films of Examples and Comparative Examples prepared above were laminated and fixed in a backlight unit for a 17-inch liquid crystal display panel (Model name: LM170E01, manufactured by Heesung Electronics, Korea), and a luminance meter (Model name: BM-7, Japan) Using TOPCON Co., Ltd., measure the luminance at any of 13 points and calculate the average value.

Hardness Measurement

A 500g load was applied using a pencil hardness tester (Yoshimitsu, Japan) and the pencil hardness was measured in accordance with 8.4.2 of JIS K5400-1990.

<Optical Interference Measurement>

Two prism films of each of Examples or Comparative Examples were placed between a plurality of glass plates, and pressure was applied to the glass plate ← to observe optical interference (Wet-out, Newton's Ring) due to excessive adhesion generated in the film. Relative evaluation was performed as follows according to the degree of occurrence of the phenomenon.

Wet-out: Occurrence ← ◎-○-△-× → Occurrence

Newton's Ring: Occurrence ← ◎-○-△-× → No Occurrence

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Luminance (Cd / ㎡) 2050 2033 1998 2010 Hardness H H HB HB Optical interference Wet-out × △ ○ ○ Newton's ring × △ ◎ ○

As a result of the physical property evaluation, the embodiment including the first light diffusing layer, the second light diffusing layer, and the prism layer according to the present invention had better luminance than Comparative Example 1 having only the first light diffusing layer, and the light diffusing layer and It can be seen that the brightness and hardness were superior to those of Comparative Examples 2 and 3 in which the prism layer was separately installed, and less light interference occurred.

Therefore, by increasing the utilization efficiency of the light source while minimizing the light loss and spreading the light twice, it can be seen that the brightness and hardness have an effect equal to or higher than when using the conventional light diffusing film and the prism film separately. .

As described above, the present invention can simultaneously provide a function of improving the brightness while evenly spreading the light emitted from the light guide plate, which significantly shortens the manufacturing process as compared with the case of separately mounting a light diffusing film and a prism film. In addition to reducing the cost, it is possible to provide a thinner liquid crystal display.

In addition, the present invention can provide a light control film that can prevent the loss of light, such as light interference phenomenon, scattering or absorption caused by laminating a plurality of films, damage to the film.

Claims (4)

Transparent substrate layer; A first light diffusion layer formed on one surface of the transparent substrate layer and including a binder resin and light diffusing particles having an average particle diameter of 0.1 to 200 μm; A prism layer formed on the first light diffusing layer; And It is formed on the rear surface of the transparent substrate layer, and a light control film comprising a second resin layer comprising a binder resin and light diffusion particles having an average particle diameter of 0.1 ~ 200㎛. The method of claim 1, The first light diffusion layer and the second light diffusion layer is a light control film, characterized in that the light diffusion particles contain 0.01 to 1000 parts by weight based on 100 parts by weight of the binder resin. delete The method of claim 1, The prism layer is a light control film, characterized in that it comprises any one selected from a linear arrangement of parallel triangular prism, a polygonal prism structure, a conical prism structure, a hemispherical prism structure and a non-spherical prism structure.

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